This predoctoral training-grant is designed to study how serotonin (5HT) precursor availability relates to measures of impulsivity and alcohol-induced aggressive behavior. Two groups of 50 women each, those with and without histories of physical fighting, will first participate in an alcohol challenge during laboratory-measured aggression. Following the challenge across aggression testing, the same women will be tested with two types of impulsivity paradigms: rapid-decision (IMT/DMT and GoStop) and reward-directed (SKIP and Two Choice) impulsivity tasks. The availability of the 5HT precursor will be measured by the ratio of tryptophan (Trp) to tyrosine, phenylalanine, valine, leucine, and isoleucine, 5 large neutral amino acids that compete with Trp for transport across the blood-brain barrier. The 5HT precursor availability will then be related to impulsivity testing and to alcohol-induced aggression. The goals are to determine whether 5HT precursor availability is related to: (1) individual differences in sensitivity to alcohol-induced aggression; (2) laboratory-measured impulsivity; and (3) physical violence demonstrated before age 15 (Fight+ and Fight). This study will lead to a better understanding of factors that contribute to individual differences observed after alcohol consumption. This project is dependent on a multidisciplinary approach and will provide training in clinical techniques, experimental design, behavioral laboratory testing, neurobiology, analytical neurochemistry, statistical analysis, arid presentation and publication preparation.